From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Spark plug insulation materials, fixing methods, and alternative washer suggestions for engine testing.
| Identifier | ExFiles\Box 34\2\ Scan088 | |
| Date | 15th May 1916 | |
| H.{Arthur M. Hanbury - Head Complaints} H.{Arthur M. Hanbury - Head Complaints} 795 a (400 T) S.C. 536. 15-5-16; G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 1546. To HS{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} -2- R8/W11916. The heat of the gases in this space, therefore, goes directly to the earthenware insulator and thence to the plug body by conduction and radiation, at the same time, there being such a small space between the earthenware and the steel body, that the volume of gas and heat units in this space must be very small. Regarding the insulation, this material is not porcelain but it is the stone ware or pot, and the nearest I know that is made in England like it is made by Bullers of Hanley, who have a very similar insulating stone ware which they use for insulating overhead telegraph wires. It is very strong and has the virtue that it does not depend upon the glaze for its insulation, but is a good insulator right through the body of the material. Regarding the fixing of the parcelain into the iron body of the plug, I think this could be fitted in with a cement probably composed partly of sodium silicate. This is not intended to take the place of washerws and burnishing but as an additional means of getting a good heat conductar between the porcelain and the stee. We have suggested on previous occasions that instead of using copper asbestos washers under the plug, you try a plain copper washer which eill conduct the heat better. We are sending instructions also for you to get a set of cylinders specially arranged with the plug in a pocket, to see whtether this would fire the engine equally as well and have any beneficial effect of keeping the oil off the plug or the temperature of the plugs lower. | ||